Quantitative analysis of defect states in InGaZnO within 2 eV below the conduction band via photo-induced current transient spectroscopy.

This work investigates the function of the oxygen partial pressure in photo-induced current measurement of extended defect properties related to the distribution and quantity of defect states in electronic structures. The Fermi level was adjusted by applying a negative gate bias in the TFT structure, and the measurable range of activation energy was extended to < 2.0 eV. Calculations based on density functional theory are used to investigate the changes in defect characteristics and the role of defects at shallow and deep levels as a function of oxygen partial pressure. Device characteristics, such as mobility and threshold voltage shift under a negative gate bias, showed a linear correlation with the ratio of shallow level to deep level defect density. Shallow level and deep level defects are organically related, and both defects must be considered when understanding device characteristics.

Characterization of the SnO2 based thin film transistors with Ga, In and Hf doping.

We investigated the effects of doping tin oxide thin film transistors (TFTs) with Ga, In, and Hf. The quantity of doping impurities added to the SnO2-TFT channel layer was as follows: Ga (6.3-21.4 at.%), In (9.6-55.6 at.%), and Hf (1.2-2.7 at.%). Hafnium and gallium doping of SnO2 thin film decreased the carrier concentration, possibly due to a decrease in field effect mobility, and reduced oxygen vacancy-related defects. Indium-doped SnO2-TFTs exhibited high performance with a high field-effect mobility of > 20 cm2 V(-1) s(-1). The current on/off ratio and the subthreshold swing of In-doped SnO2-TFTs was 1 x 10(9) and 0.5 V/decade, respectively. These results demonstrate that Ga, In, and Hf doping can effectively enhance the performance of SnO2-based TFT devices.

Characteristics of tin oxide-based thin film transistors prepared by DC magnetron sputtering.

Here we demonstrate the fabrication of SnO(x) thin-film transistors (TFTs), where SnO(x) thin films are deposited as an active channel layer by DC magnetron sputtering. We analyzed the effects of the oxygen partial pressure ratio and post-deposition heat treatment (PDHT) on the characteristics of the SnO(x) thin films. We found improved performance of the TFTs obtained by using interface modification with the optimized deposition condition of SnO(x) thin films. These results are helpful for fabricating oxide-TFTs, including simple binary oxide semiconductors, as an active channel layer.

Al2O3/TiO2 multilayer passivation layers grown at low temperature for flexible organic devices.

In this study, the permeability of passivation layers consisting of aluminum oxide (Al2O3) and titanium oxide (TiO2) was examined. The films were deposited on poly(ether sulfone) (PES) substrates via electron cyclotron resonance atomic layer deposition (ECR-ALD) at various deposition temperatures. The optimum plasma power and deposition temperature were investigated through measurements of the refractive index and packing density of the Al2O3 and TiO2 films. A buffer layer/multilayer structure was proposed in this study to improve the passivation barrier performance. A low water vapor transmission rate (WVTR) of approximately 5 x 10(-3) g/m2 x day was achieved with two Al2O3/TiO2 stacks with thicknesses of 40 nm deposited at 80 degrees C. Based on the Arrhenius rate equation, the activation energy of water vapor transmission through different passivation structures was examined. The activation energies of Al2O3, Al2O3/TiO2, and two Al2O3/TiO2 stacks with thicknesses of 40 nm were 51.8, 63.9, and 74.7 kJ/mol, respectively.

High performance thin film transistor with ZnO channel layer deposited by DC magnetron sputtering.

Research in large area electronics, especially for low-temperature plastic substrates, focuses commonly on limitations of the semiconductor in thin film transistors (TFTs), in particular its low mobility. ZnO is an emerging example of a semiconductor material for TFTs that can have high mobility, while a-Si and organic semiconductors have low mobility (<1 cm2/Vs). ZnO-based TFTs have achieved high mobility, along with low-voltage operation low off-state current, and low gate leakage current. In general, ZnO thin films for the channel layer of TFTs are deposited with RF magnetron sputtering methods. On the other hand, we studied ZnO thin films deposited with DC magnetron sputtering for the channel layer of TFTs. After analyzing the basic physical and chemical properties of ZnO thin films, we fabricated a TFT-unit cell using ZnO thin films for the channel layer. The field effect mobility (micro(sat)) of 1.8 cm2/Vs and threshold voltage (Vth) of -0.7 V were obtained.

Titanium dioxide thin films deposited by plasma enhanced atomic layer deposition for OLED passivation.

Plasma enhanced atomic layer deposition (PEALD) of titanium dioxide thin films was conducted using Tetrakis dimethylamino titanium (TDMATi) and an oxygen plasma on a polyethersulfon (PES) substrate at a deposition temperature of 90 degrees C. The effects of the induced plasma power on passivation properties were investigated according to film thickness. The growth rate of the titanium dioxide film was 0.8 A/cycle, and the water vapor transmission rate (WTVR) for a 80 nm titanium dioxide film was 0.023 g/m2 day. The passivation performance of the titanium dioxide film was investigated using an organic light-emitting diode (OLED). The coated OLED lifetime was 90 h, 15 times longer than that of an uncoated sample.